Retractable knife



FIG. 1 is a perspective view of a retractable knife showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a left end view thereof;

FIG. 7 is a right end view thereof;

FIG. 8 is a sectional view taken along a line 8--8 in FIG. 3; and,

FIG. 9 is an cross-sectional view taken along a line 9--9 in FIG. 2. 

The ornamental design for a retractable knife, as shown and described. 